1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Determine The Speed of a Charge at a given point

  1. Feb 9, 2015 #1
    1. The problem statement, all variables and given/known data
    Given: The electric potential function: V= 3x^2 + 2xy +(y^2)z + 20
    a) A 4 coulombs, 2kg charge is released from the origin. Determine the speed of the charge at (1,1,-1)

    2. Relevant equations
    Kinetic Energy= 1/2 mv^2

    3. The attempt at a solution
    I tried to use the fact that the change in potential energy is equal to the negative change in kinetic energy.
    I calculated the change in electric potential to be 4 V and set that equal to the negative change in kinetic energy, which would just be -1/2 mv^2
    However, when I solve for the velocity, I get the square root of negative 4. Have I done something wrong or is the problem just flawed?
  2. jcsd
  3. Feb 9, 2015 #2


    User Avatar
    Homework Helper
    Gold Member
    2017 Award

    I think you're right. The question is flawed. A positive charge will not go from lower to higher potential without some external force.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted